Development of Ordered Poly(aspartic Acid)-Oleic Acid Coatings with Enhanced Antimicrobial Activity: A Proof-of-Concept Study

The leading cause of post-surgical hospital readmission is the emergence of hospital-acquired infections (HAIs), where surgical site infections (SSIs) constitute a substantial negative impact on patient outcome and contribute annual direct costs estimated to range from $28.4 billion to $45 billion in the U.S. To address the need for novel antimicrobial coating strategies, previous research has demonstrated that certain microbes can degrade poly(aspartic acid) (PAA)-based coatings, suggesting potential limitations of single-compound approaches that must be considered when designing antimicrobial surfaces. In this proof-of-concept study, we investigated whether ordered sequential coatings combining thermally synthesized PAA (tPAA) and oleic acid (OleA) might produce enhanced antimicrobial effects compared to individual compounds. Despite concerns regarding PAA biodegradability, the benefits of using PAA include low cytotoxicity and an ability to chelate metals such as calcium and facilitate bone mineralization and growth post-surgery. Using simple yet effective methods of surface coating applications which utilize tPAA and OleA, we investigated the potential of these ordered coatings to attenuate planktonic and sessile (biofilm) growth and development in Pseudomonas aeruginosa and Escherichia coli in vitro. Application of these ordered coatings resulted in up to 62% reduction in bacterial carrying capacity for P. aeruginosa and up to 43% reduction in biofilm mass relative to untreated controls. Further, confocal imaging via immunohistochemical labeling revealed methods for evaluating the impact of treatments targeting biofilm development through extracellular DNA quantification. Additionally, these coatings show dose-dependent cytotoxic effects against 3T3 mouse fibroblast cells. These preliminary findings, along with results derived from cytotoxicity assessment and physicochemical characterization via dynamic light scattering, suggest that ordered tPAA-OleA coating systems warrant further investigation as potential antimicrobial strategies, though additional validation, including testing against diverse clinical isolates, mechanistic studies, and in vivo evaluation, would be required before clinical application.